LABORATORIO DE ANÁLISIS POR LABORATORIO DE ANÁLISIS POR ACTIVACIÓN NEUTRÓNICA (LAAN)ACTIVACIÓN NEUTRÓNICA (LAAN)

NUCLEACLEAR ENGINEERING DEPARTMENT

CENTRO ATÓMICO BARILOCHEATÓMICO BARILOCHE

COMISIÓN NACIONAL DE ENERGÍA ATÓMICA

ARGENTINA

RA-6 reactorRA-6 reactor

Main Purpose: Teaching for the School of Nuclear Engineering at Instituto Balseiro

ther in core: 7x1012 n.cm-2.s-1 (max)

Others: NAA personnel training material testing

Beams : Boron Neutron Capture Therapy (BNCT) NeutrographyPGNAA

Operation & core configuration: on request

FACILITIES FOR NAA: RA-6FACILITIES FOR NAA: RA-6

Neutron Activation Analysis Laboratory Neutron Activation Analysis Laboratory (LAAN)(LAAN)

Sergio RIBEIRO GUEVARA Eric DORVALMaría ARRIBÉRE

“Consultants” Abraham KESTELMAN nucl. measurem.Erhard ACHTERBERG nucl. data evaluation

RA-6RA-6

Francisco LESZCZYNSKI

FACILITIES FOR NAA: RA-6FACILITIES FOR NAA: RA-6Only Instrumental NAAOnly Instrumental NAA

At RA-6:

irradiation boxes

1 pneumatic transfer system (1 sec. traveling time)

10% eff. HPGe (n-type) + electronics

In 2 wooden “buildings”, for low background counting

30% eff. HPGe (p-type) + electronics

LO-AX HPGe (planar) + electronics

Biological and geological sample preparation rooms

NEUTRON FLUX MEASUREMENTSNEUTRON FLUX MEASUREMENTS

RA-6 started operation in 1983 Fuel: originally 93% enriched U from RA-3 Neutron spectrum was characterized between 1990-1992 in four

irradiation positions (E5, F5, D8, I6) and was followed until now.

Expected re-fueling: May-August? 2006Fuel: 20% enriched UThe neutron spectrum has to be characterized in at least two

positions (E5, I6) or equivalents.Good news: the fuel is fresh, the history will be well known

90’s calibration for the parametric 90’s calibration for the parametric methodmethod

Goal: estimate elemental concentrations from integral nuclear parameters

Høgdahl + Wescott conventions, assuming almost isotropic flux

Measurement of working cross sections for some particular reactions

Routine: irradiations with monitors for thermal, epithermal and fast neutrons

For short irradiations: Mn, Au, AlFor intermediate irradiations: Sc, Au, Al or NiFor long irradiations (>10 h): Co, Au, Ni

Gamma self shielding: easy to addressNeutron self shielding: were estimated and, if significant, avoided

90’s calibration for the parametric 90’s calibration for the parametric methodmethod

“multielement” flux calculation

Slope: 0/I*

TOOLSTOOLS

PC 3.4 GHz processor, 2 GB DDRM, 120 Gb HD, 800 MHz bus

Software: Mandrake 10.1 Community Linux Platform

Applications taken from libraries under the GNU public license

Differential cross sections from ENDF-VI and JEF-2.2 libraries

Nuclear grade materials for activation measurements

RA-6: MCNP code

Planned approachPlanned approach

The first positions to be characterized are in the core center, where flux is expected to be isotropic

The assumptions for the flux characterization in the core center are: linear anisotropy flux modeled by Maxwell+ 1/E joint by the Horowitz-Tretiakoff

function

the response functions will be computed using the differential cross sections with data taken from current libraries

validation by irradiation of monitors

Neutron self shielding, Cd factors, foil borders effects are computed when needed

Planned approachPlanned approach

Au, almost independent of the “joint function” or Cd cut-off Co, slight dependence on the “joint function” and/or Cd resonances Mn, dependent of the “joint function” and/or Cd resonances Sc, dependent of the “joint function” and the Cd cut-off

Next irradiations: first check on the modeling. All monitors bare and under different cadmium thicknesses

MCNP: a handout with his first calculations for the Fe and i6 irradiation positions has been prepared.

First choice of monitors:

Planned approach + CRPPlanned approach + CRP

To be defined…

Comparison of the analytical flux with MCNP for the core center and reflector

Explore the possibility to perform corrections for neutron self attenuation and cadmium factors by MCNP

Obtain a better estimate the effect of the sample irradiation can and other containers